Chapter 3 Flashcards
(25 cards)
What are synapses?
Specialized junctions where axons contact dendrites of other neurons, allowing signal transmission.
What are the two components of a synapse?
Presynaptic nerve ending and postsynaptic component, often on a dendritic spine.
How is the signal transmitted across the synaptic gap?
By chemical messengers called neurotransmitters, not by electrical currents.
Where are neurotransmitters stored?
In synaptic vesicles inside the presynaptic terminal.
What triggers the release of neurotransmitters?
The arrival of an action potential, which opens calcium (Ca²⁺) channels.
What do presynaptic proteins like SNARE, synaptotagmin, and synaptobrevin do?
They help vesicles fuse with the membrane and release neurotransmitters.
What happens to synaptic vesicles after releasing neurotransmitters?
They are recycled—refilled and reused.
What is the synaptic cleft?
A 20 nm gap across which neurotransmitters diffuse to reach the postsynaptic cell.
What are receptors on the postsynaptic membrane?
Molecular structures that bind neurotransmitters and trigger a response.
How is the synaptic cleft cleared of neurotransmitters?
By glial cell transporters, reuptake by neurons, or enzymatic breakdown.
What are ionotropic receptors?
Receptors that directly open ion channels when neurotransmitters bind.
What is an EPSP?
An excitatory postsynaptic potential; caused by Na⁺ or Ca²⁺ influx, depolarizing the membrane.
What is an IPSP?
An inhibitory postsynaptic potential; caused by Cl⁻ influx or K⁺ efflux, hyperpolarizing the membrane.
What determines whether a neuron fires?
The sum of EPSPs and IPSPs — if the threshold is reached, an action potential is generated.
What are metabotropic receptors?
Receptors that activate G-proteins and second messengers instead of ion channels.
How do metabotropic effects differ from ionotropic?
Metabotropic effects are slower, longer-lasting, and modulate neuron activity rather than triggering action potentials.
What is a second messenger?
An intracellular molecule activated by G-proteins to propagate the signal inside the neuron.
What is the main excitatory neurotransmitter in the brain?
Glutamate
What are the main inhibitory neurotransmitters?
GABA and Glycine
What does acetylcholine do?
Acts on both ionotropic (e.g., at neuromuscular junctions) and metabotropic receptors (e.g., modulating attention).
What does dopamine do?
Modulates reward and emotional processing in the brain.
What does noradrenaline do?
Helps respond to stress and novelty, coordinating widespread neural responses.
Where are noradrenaline neurons located?
In the locus coeruleus, projecting throughout the brain and spinal cord.
Why are neuromodulatory neurons so influential despite being few in number?
Their axons project widely, allowing broad influence on many brain regions.
